Explore the technical specs of ITEQ IT-998, the Super Ultra-Low Loss PCB material for 800G Ethernet. Learn about its Df​ of 0.0020, 112G/224G SI tips, and fabrication guides.
In the high-stakes world of hyperscale data centers and AI computing clusters, we have officially moved past the era where signal integrity (SI) can be “fixed” solely through silicon equalization or heavy-duty retimers. As the industry transitions from 400G to 800G Ethernet and beyond, the Nyquist frequency for 112G and 224G PAM4 signaling has climbed so high that the PCB substrate itself has become the most significant bottleneck in the signal path.
The ITEQ IT-998 series represents a quantum leap in laminate technology. Classified as a “Super Ultra-Low Loss” (SULL) material, it is specifically engineered to handle the extreme attenuation and phase-skew requirements of next-generation networking. When you are working with a unit interval (UI) so small that every millimeter of trace length contributes to a potential eye closure, you need a dielectric that acts more like air and less like an insulator.
This guide provides a deep-dive engineering analysis into the ITEQ IT-998 series, exploring its resin chemistry, electrical specifications, and the specialized fabrication nuances required to yield 32+ layer 800G backplanes.
The Chemistry of IT-998: Solving the Polarity Problem
To achieve a Dissipation Factor (Df​) in the range of 0.0010 to 0.0020, ITEQ had to fundamentally rethink the epoxy-polyphenylene ether (PPE) resin matrix. Standard high-speed materials contain polar molecular groups that oscillate when exposed to high-frequency electromagnetic fields. This oscillation converts electrical signal energy into waste heat—the primary cause of dielectric loss.
The ITEQ IT-998 utilizes a highly advanced, low-polarity resin system. By reducing the density of these polar groups, ITEQ has created a substrate that is nearly “invisible” to high-frequency waves. Furthermore, the material is designed for Halogen-Free compliance without sacrificing thermal stability. It achieves a UL 94 V-0 rating through a reactive phosphorus-based system that actually strengthens the polymer cross-linking, resulting in a staggering Decomposition Temperature (Td​) of 405∘C.
ITEQ IT-998 Datasheet: Core Engineering Specifications
When drafting a stackup for an 800G switch fabric or a liquid-cooled AI accelerator, the raw numbers dictate your trace geometries. Below are the critical datasheet metrics for the IT-998 laminate, aligned with IPC-TM-650 testing methodologies.
Table 1: Thermal and Mechanical Properties
| Material Property | Test Method (IPC-TM-650) | Typical Value | Unit |
| Glass Transition Temp (Tg​) | 2.4.25 (DSC) | 185 – 195 | ∘C |
| Decomposition Temp (Td​) | 2.4.24.6 (5% wt loss) | 405 | ∘C |
| Z-Axis CTE (Pre-Tg) | 2.4.24 | 40 | ±è±è³¾/∘C |
| Z-Axis CTE (Post-Tg) | 2.4.24 | 220 | ±è±è³¾/∘C |
| Total Z-Axis Expansion (50-260$^\circ\text{C}$) | 2.4.24 | 2.1 | % |
| Thermal Resistance (T288 / T300) | 2.4.24.1 | > 60 | Minutes |
| Moisture Absorption | 2.6.2.1 | 0.10 | % |
| Peel Strength (HVLP Copper) | 2.4.8 | 3.5 – 4.5 | lb/inch |
| Flammability Rating | UL 94 | V-0 | Rating |
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Table 2: Electrical Performance (Typical 50% Resin Content)
The IT-998 series is available in standard and “SE” (Special Edition) versions, with the latter utilizing Low-Dk Glass.
| Frequency | Dielectric Constant (Dk​) | Dissipation Factor (Df​) |
| 1 GHz / 2 GHz | 3.50 | 0.0019 |
| 5 GHz / 10 GHz | 3.45 | 0.0020 |
| 20 GHz / 30 GHz | 3.42 | 0.0021 |
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Engineering Note: A Df​ of 0.0020 at 10 GHz is the gold standard for 800G designs. At these levels, the dielectric loss is so low that the smoothness of your copper foil (conductor loss) becomes the dominant factor in your total link budget.
Signal Integrity Challenges at 800G: Skew and Skin Effect
Specifying ITEQ IT-998 is the first step, but at 800G (112G/lane), the material’s bulk properties can be undermined by poor layout or incorrect glass selection. As an SI engineer, you must address Glass Weave Skew and Copper Profile.
Managing Glass Weave Skew (GWS)
In 112G PAM4 signaling, the unit interval (UI) is so short that a skew of just 1-2 picoseconds between the P and N legs of a differential pair can destroy the eye diagram. Standard E-glass fabric has “knuckles” and “gaps” where the Dk​ varies significantly.
Solution: ITEQ IT-998 should almost always be specified with Spread Glass (Square Weave) prepregs, such as styles 1067 or 1078. Even better, use the IT-998 version paired with Low-Dk Glass (NE-glass). Because the Dk​ of Low-Dk glass is much closer to the resin Dk​, the “permittivity delta” is minimized, drastically reducing intra-pair skew without needing expensive trace rotation.
Conductor Loss and HVLP Copper
At 28 GHz and 56 GHz (Nyquist frequencies for 112G/224G), the “skin effect” forces the signal to travel on the extreme outer surface of the copper. If the copper is rough, the signal path length increases, and loss skyrockets.
Requirement: Pair IT-998 with HVLP (Hyper Very Low Profile) copper foil (Rz​<1.5μm).
Adhesion Note: Because HVLP copper is so smooth, it is harder for the resin to “grip” the metal. The IT-998 resin is chemically modified to provide a peel strength of ~4.0 lb/inch even on ultra-smooth foils, preventing delamination during reflow.
Advanced Fabrication for High-Layer Count 800G Backplanes
Building an 800G switch usually involves a 24 to 36-layer board that is 3mm to 5mm thick. This introduces massive manufacturing risks. When you specify IT-998, you are selecting a material designed for these high-aspect-ratio challenges.
Restricted Z-Axis Expansion (2.1%)
Via barrel cracking is the #1 killer of thick backplanes. During lead-free reflow, the board swells vertically. If the material expands too much, it tears the copper plating inside the via. IT-998 restricts expansion to 2.1%, which is significantly better than standard High-Tg materials. This ensures via integrity through multiple SMT cycles and potential rework.
Drilling and Desmear
The high-performance fillers in IT-998 are abrasive.
Drilling: Fabricators must use carbide drills with controlled hit counts to prevent “wicking” or rough hole walls.
Desmear: Due to the chemical resistance of the Super Ultra-Low Loss resin, standard permanganate desmear might be insufficient. Plasma Desmear is highly recommended to ensure perfectly clean via barrels before plating.
Dimensional Stability and Registration
In 30-layer boards, layer-to-layer registration is a nightmare. IT-998 is designed with high dimensional stability, meaning the cores don’t “shift” or shrink unpredictably during the lamination press. This allows fabricators to maintain tight annular ring requirements for high-density ASIC breakouts.
Comparative Analysis: IT-998 vs. The Market
| Feature | ITEQ IT-968 | ITEQ IT-988G | ITEQ IT-998 | Rogers RO1200 |
| Loss Category | Very Low Loss | Ultra Low Loss | Super Ultra-Low Loss | Extreme Low Loss |
| Df​ @ 10 GHz | 0.0050 | 0.0028 | 0.0020 | 0.0017 |
| Target Data Rate | 100G / 400G | 400G / 800G | 800G+ / 224G PAM4 | 800G+ / 1.6T |
| Tg​ (DSC) | 185∘C | 190∘C | 190∘C | 290∘C |
| Fab Complexity | Standard | High-End PWB | Advanced SULL | Specialized / PTFE |
Export to Sheets
The IT-998 provides a “sweet spot” for 800G. It offers electrical performance that rivals specialized PTFE/ceramic materials but can be processed in a standard high-end multilayer PCB facility, significantly reducing the Total Cost of Ownership (TCO).
Optimal Applications for IT-998
800G / 1.6T Networking Switches: Core routers and fabric cards using 112G/lane SerDes.
AI Training Clusters: High-bandwidth CPU-to-GPU and GPU-to-GPU fabrics (NVLink/Infinity Fabric).
High-Speed Test Equipment: VNA interface boards and high-frequency bit-error-rate testers (BERT).
Optical Modules: High-density transceivers (QSFP-DD800 and OSFP).
Useful Resources and Industry Databases
To ensure your 800G stackup is mathematically sound, integrate the following:
ITEQ Global Material Selector: Download construction-specific Dk​ tables (e.g., for 1067 vs 3313 glass).
IPC-4101 Specification: IT-998 meets slash sheets /102 and /103 for halogen-free, ultra-low loss materials.
Saturn PCB Design Toolkit: Use this to calculate via current capacity and thermal limits for IT-998’s 190∘C Tg​.
Polar Instruments Speedstack: Most tier-1 fabricators have IT-998 in their library for accurate impedance modeling including copper roughness compensation.
Conclusion: Designing for the 224G Horizon
The ITEQ IT-998 is not just another board material; it is a specialized engineering solution for the most difficult signal integrity challenges in modern computing. By offering a stable Dk​ of 3.45 and a Super Ultra-Low Df​ of 0.0020, it provides the headroom necessary to transition from 400G to 800G and beyond.
For the PCB engineer, IT-998 offers the peace of mind that signals will arrive with wide-open data eyes, even across long backplane traces. When paired with Spread Glass and HVLP copper, IT-998 is the foundation upon which the future of the internet is being built.
Frequently Asked Questions (FAQs)
1. Is ITEQ IT-998 compatible with Lead-Free assembly?
Yes. With a Td​ of 405∘C and a Tg​ of 190∘C, IT-998 is exceptionally robust. It can withstand 6-10 lead-free reflow cycles at 260∘C without blistering or delamination, making it ideal for complex double-sided SMT and rework.
2. What is the difference between IT-988G and IT-998?
The IT-988G is an “Ultra Low Loss” material (Df​≈0.0028), while IT-998 is “Super Ultra-Low Loss” (Df​≈0.0020). While they look similar on paper, IT-998 provides the extra margin needed for longer 112G/224G trace reaches.
3. Does IT-998 require special copper foil?
To realize the full benefits of the SULL resin, you must use HVLP (Hyper Very Low Profile) or better copper. Using standard RTF copper with IT-998 is a waste of money, as the conductor loss will negate the dielectric loss improvements.
4. Can I use IT-998 for hybrid stackups?
Absolutely. Many 800G designs use IT-998 for the top/bottom signal layers and internal high-speed layers, while using a more cost-effective material like IT-180A for power/ground layers to manage total board cost.
5. Why is moisture absorption (0.10%) so important at 800G?
Water has a Dk​ of approximately 80. If a material absorbs even a tiny amount of moisture, the Dk​ and Df​ of the trace will shift, causing impedance mismatches and increased loss. IT-998’s ultra-low absorption ensures signal stability in all environmental conditions.
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